Electric switch



Dec. 17, 1929. c. L. JONES' 1,740,307

ELECTRIC SWITCH Filed April 7, 1924 INVENTOR named D... 11, 1929 UNITEDSTATES PATENT OFFICE ELECTRIC SWITCH Application filed April 7 Thepresent invention relates to' electric switches, and more .especially tomeans for prevention of arcing at the switch contacts.

A non-flammable liquid or gas, preferably 5 carbon dioxide, isintroduced under pressure between the contacts. The contacts areseparated by the pressure thus supplied. The expanding gas or.gasifiedliquid also serves to blow out the arc.

In the drawings Figure 1 is a vertical section through the switchillustrating one embodiment of the invention;

Figure 2 is a detail section through the low er end of the hollowcontact, and I Figure 3 is a horizontal section along the line III-IIIof Figure 1.

Referring to the illustrated embodiment of the invention the switchcomprises two separable contacts 1 and 2. The upper contact 1, which isshown as the fixed contact, is hollow, having a passage 3-ext'endingthrough it to the contact faces of the contacts 1 and 2. The lowercontact 2 is a solid movable contact normally held against the contact 1by means of a spring 4. A latch 5 engaging a tooth 6 1n the contact 2 isprovided for removably holdingthe contacts separated. The contact 2 iscarried on a frame 7 which is connected to the line in which the switchis interposed, and which is carried by any suitable insulating means 8to insulate it from the contact 1 and its operating parts.

The contacting ends of the contacts 1 and 2 are enclosed in atube 9 ofan insulatin material which is resistant to thermal s ock. This tube 9is preferably made up of a plurality of fused silica or quartz segments10 shown in section in Figure 3. These are bound together by suitablemetal bands 11 for structural strength. The quartz tube 9 is in sertedin a recess in the insulator 12, which may be made of porcelain or anyother-suitable insulating material.

The switch contacts are separated by the pressure caused by introducingliquid carbon dioxide or other fluid between their'contact ing faces.The liquid carbon dioxide is, of course, under high pressure. Thepressure of the carbon dioxide shoots the contact 2 at 1924. Serial No.704,622.

high velocity downwardly from the tube 9 somewhat after the manner inwhich a projectile is discharged from a gun.

The carbon dioxide is introduce-d between the contacting faces ofthecontacts 1 and 2 through the passage '3 in the contact 1. A- smallreservoir 13 is provided at the end of the passage 3 for holding asupply of liquid carbon dioxide 14. The reservoir 13 is supplied througha pipe 15 from a carbon dioxide storage container (not shown). The pipe15 is preferably provided with an orifice 16 to limit the rate of flowfrom the carbon dioxide storage container into the reservoir 13. Anysuitable valve arrangement may be employed for dioxide through thepassage 3 between the contacts 1 and 2. The liquid carbon dioxide is, ofcourse, under the high pressure in which it is supplied in the storagecontainers. lVhen the valve 17 is opened, the pressure of the carbondioxide drives the contacts 1 and 2 apart.

Any heat whichmay be generated by arcing between the contacts at themoments of separation tends to volatilize or expand the carbon dioxide.At the moment of separation of the contacts, the carbon dioxide betweenthem is under a considerable pressure, which of itself tends to preventelectric discharge taking place. Also the stream of carbon dioxidebetween the contacts tends to violently blow out or sweep away any arewhich may tend to form between the contacts. The cooling effect of theexpanding carbon dioxide also tends to produce a condition unfavorableto the formation and maintenance of an electric arc.

When the movable contact 2 is shot down, it is engaged by the latch 5and held out of contact with the fixed contact 1 until such time as itmay be desired to close the switch.

On account of the extreme temperature conditions produced by theformation of an arc followed immediately by the intense cold of theexpanding carbon dioxide. the tube 9 should be made of some insulatingmaterial which is resistant to thermal shock, and for this purpose Iprefer to use fused silica, although it is to be understood that othermaterials may be used.

WVhile I prefer to use liquid carbon dioxide as the material to beintroduced between the contacts,other'non-aqueousfiuids,eitherliquid orgaseous, may be-employed. WVater is not suitable for this purpose,particular-l when high voltages are to be handled. Sue fluids should benon-flammable, non-corrosive and non-conducting, and may be compressedinert gas, such as nitrogen or a volatile liquid under pressure, such ascarbon tetrachloride or other fluids containing halogenatedhydrocarbons.

\Vhile the drawing illustrates diagrammatically an embodiment of theinvention, it is to be understood that it may be embodied in other formsof switches, in which any of the usual mechanisms may be employed formounting the contacts and. operating them on any desired duty cycle.

The present invention is therefore not; limited to its specific andpreferred embodiment shown in the drawings and above described indetail, but may be otherwise embodied within the scope of the followingclaims.

I claim:

1. An electric switch comprising separable contacts, a tube of materialresistant to thermal shock surrounding the contacts, and means forsupplying a highly compressed non-flammable non-conducting fluid betweenthe contacts so as to separate them by the pressure thus applied.

2. An electric switch comprising separable contacts, a tube of materialresistant to thermal shock surrounding the contacts, and means forintroducing liquid carbon dioxide between the contacts so as to separatethem by the pressure of the carbon dioxide.

3. A tube for withstanding thermal shock comprising a plurality ofsilica segments, and means for holding them together.

4. A tube for withstandin thermal shock comprising a plurality of si icasegments. a band for holdin the segments together, and a casing surrouning the silica segments.

5. A tube for withstanding thermal shock comprising a plurality ofsegments of a material havmg a low co-efiicient of thermal expansion,and means for holding the segments together.

6. An electric switch comprising se arable contacts, and means forseparating t e contacts and blowing out any are by the injection of acompressed non-inflammable non-conducting liquid of boiling point below0 C. between the contacts when the contacts are in closed position.

7. An electric switch comprising separable contacts, a chambersurrounding the contacts and in which at least one of the contacts ismovable, and means for introducing into the chamber between the contactsa'non-infiamjmable non-conducting fluid of boiling point below 0 C.under pressure so as to both drive the contacts apart and blow out anyare formed upon their separation.

8. An electric switch comprising separable contacts, a chambersurrounding the contacts and in which at least one of the contacts ismovable, and means for introducin into the chamber between the contactswhi e the contacts are in closed position, carbon dioxide under pressureequal to, or greater than, its vapor pressure so as to both drive thecontacts apart and blow out any are formed upon their separation.

9. An electric switch comprising separable contacts, and means 'forsupplying liquid carbon dioxide between the contacts as they areseparated whereby a stream of intensely cold carbon dioxide gas isdischarged across the contacts to chill and blow out any incipient areformed upon their separation.

10. Anelectric switch comprising separable contacts, and means fordischarglng high- 1y compressed carbon dioxide between the contacts toseparate the contacts and to chill and blow out any incipient are formedupon their separation.

11. An electric switch having separable contact faces, and means fordischarging highly compressed carbon dioxide against one of the contactfaces to separate the contacts and chill and blow out any incipient areformed upon their separation.

In testimony whereof I have hereunto set my hand. CHAS. L. JONES.

